Photographic silver halide emulsions



Patented Sept. 21, 1 948 PHOTOGRAPHIC SILVER HALIDE EMULSION S RalphKingsley Blake, Parlin, N. J., assignor to E. I. du Pont de Nemours &Company, Wilmington, Del, a corporation of Delaware No Drawing.Application May 4, 1945, Serial No. 592,057

8 Claims.

This invention relates to photographic silver halide emulsions ofimproved stability. More particularly it relates to photographic silverhalide emulsions and emulsion layers which contain small amounts oflower monoalkylaminomonohydroxybenzenes.

Photographic elements deteriorate upon aging and ordinarily should beused within a year or two after manufacture if one is to obtainsatisfactory results. This means that photographic elements should beused within such period in order to obtain good results. Thedeterioration of photographic elements upon aging generally results in achemical fog which aflects the sensitivity and developability thereof.The formation of this fog is accelerated by the advance of time andtemperature. Many proposals for controlling chemical fog have been madeand while some are meritorious they involve the use of chemicals whichare not always readily available. Others while improving the stabilityof emulsion layers decrease the sensitivi-ty.

An object of this invention is to provide photographic silver halideemulsions of satisfactory stability. A further object is to provide suchemulsions without deleteriously affecting their sensitivity to light. Arelated object is to provide photographic films, plates, and paperswithsilver halide emulsion layers which remain stable for long periods oftime in hot climates. Another obiect is to provide a simple andeconomical means for stabilizing silver halide emulsion layers. Stillother objects will be apparent from the following description of theinvention.

The above objects are accomplished by incorporating with acolloid-silver halide emulsion a small amount of a lowermonoalkylaminomonohydroxybenzene. The alkyl group attached to. the aminonitrogen atom may contain from 1 to 2 atoms. The monoalkylaminomonohydroxybenzenes may be used in the form of the base or in the formof an addition salt, e. g., the hydrochloride or sulfate. The salts arepreferred because of their stability and increased solubility in water.

The above compounds may be added at various stages during themanufacture of colloid silver halide emulsions or dispersions r emulsionlayers but are preferably added to the emulsions prior to coating. Thealkylaminohydroxybenzene compounds may be added to an aqueous colloidsolution, such as gelatin, and mixed with a colloid silver halideemulsion or the colloid solutions may be used as a substratum coatingthe alkylaminohydroxybenzenes with the emulsion layers would be to bathea silver halide emulsion layer with an aqueous solution containing suchcompounds.

To be more specific, colloid silver halide emulsions essentiallycomposed of silver bromide and especially those containing smallamounts, e. g., 0.5 to: 10% of silver iodide may be effectivelystabilized by the addition of from 0.0015 to 0.03 gram of a lowermonoalkylaminomonohydroxybenzene per grams 'of silver halide. Thecompounds when used in these small amounts do not exhibit anydiscernible developing action upon exposed silver salts when elementscontaining the same are immersedin an alkaline solution, e. g., causticsoda solution of 1 per cent strength. Small amounts of alkaline sulfite,e. g., sodium sulfite, potassium sulfite, ammonium sulfite, etc., forinstance, about 10' to 50 times that of the alkylaminohydroxybenzenecompound are desirable in the emulsions because:

it prevents a possible loss in speed. The compounds, however, do reducethe general or chemical fog to a marked extent and increase thestability of the emulsion layers upon aging. The

compounds do not have any significant effect upon the sensitivity of theemulsionlayersand have a. fog inhibiting action.

The invention will be further illustrated but is not intended to belimited by the following examples. The parts are by weight.

To portions of a gelatinoesilver halide emulsion containing. 6.8 percent molar silver iodide and 93.2 per cent molar silver bromide and asmall amount of sodium sulfite were added the N-methyl-para-aminophenolsulfate grams 0.8 Hydroquinone do- 1.0 Sodium sulfite (anhydrous) do 900Borax do 3.0 Potassium bromide do 0.1

Water to "liters; 1

for 7 minutes at 68 F. with the results listed in the following table:

Fresh-film tested fresh Room-film held approximately 1 week at roomtemperature after coating before testing O venfllm held approximately 1week at 120 F. after coating before testing EXPERIMENT No. 1

N'-methylpara-amino- Film Relative phenol sulfate Age Speed Gamma FogFresh. 528 75 13 Control Rcom 400 71 16 Ovenm. 264 65 .33 Fresh. 493 7910 0.0025 g Room... 400 73 .06

ven. 325 74 15 Fresh. 493 76 07 00050 g Room 400 76 07 Oven 303 71 .15

EXPERIMENT N0. 2

N-methyl-para-amino- Film Relative phenol sulfate Age Speed Gamma TogFresh 400 78 14 Control Room 373 78 10 Oven 214 70 31 Fresh 400 78 120.0050 g Room 373 78 10 Oven 283 71 21 Fresh 373 78 12 0.0067 g Room 30375 .09 Oven 264 72 15 Fresh 373 .76 12 0.0083 g Room 325 .76 09 Oven 28378 15 Similar results were obtained without the sulfite with aninsignificant loss in speed.

In place of the particular monoalkylaminomonohydroxybenzene compounddescribed in the above experiments there may be substituted variousother salts coming within this class. Suitable additional compoundsinclude N-methyl-paraaminophenol hydrochloride, N-ethyl-para-aminophenolsulfate, N ethyl para aminophenol, N methyl-para-aminophenol, N-methylpara-- aminophenol hydrochloride.

Various emulsion components may be used in conjunction with the.monoalkylaminomonohydroxybenzenes. For example, color formers,hardeners, sensitizing dyes, wetting agents, fog inhibitors, and thelike may be'present in the emulsion in addition to the silver salts andthe monoalkylaminomonohydroxybenzenes, General emulsion sensitizers,such as sodium sulfite, may advantageously be used with such compounds.A suitable emulsion, for example, may contain in addition to thegelatin, silver iodide and silver bromide, small amounts of thymol,alkali sulfite, alcohol, a cyanine dye, a soluble bromide, saponin, andalum.

Colloid binding agents other than gelatin may be used in the emulsionsand emulsion layers. Suitable additional hydrophilic colloids includealbumin, polyglycuronic acid, hydrophilic cellulose derivatives, e. g.,ethers and carboxylic acid esters, vinyl alcohol polymers andinterpolymers and polyamides. These colloids may be substituted in wholeor in part for the gelatin.-

The invention has many advantages.

It provides a means for obtaining stable emulsions and emulsion layersin a simple and economical manner. Another advantage resides in the factthat photographic elements containing such emulsions are readilyobtained without any significant loss in sensitivity. A furtheradvantage resides in the fact that the novel elements have goodstability in hot climates.

As many widely different embodiments of this invention can be madewithout departing from the spirit and scope thereof, it is to beunderstood that the invention is not to be limited except as defined bythe claims. J

What I claim is: y

l. A colloid silver bromide emulsion containing from 0.0015 to 0.03 gramof N-alkylaminomonohydroxybenzene having from 1 to 2 carbon atoms in thealkyl radical per grams of silver halide.

2. A gelatino-silver iodobromide emulsion containing from 0.0015 to 0.03gram of N-alkyl-paraaminophenol having from 1 to 2 carbon atoms in thealkyl group per 100 grams of silver halide.

3. A gelatino-silver iodobromide emulsion layer containing from 0.0015to 0.03 gram of N-methylpara-aminophenol sulfate per 100 grams of silverhalide.

4. A gelatino-silver iodobromide emulsion layer containing from 0.0015to 0.03 gram of N-methylpara-aminophenol sulfate and a small amount ofan alkaline sulfite per 100 grams of silver halide.

5. A photographic element bearing at least one hydrophiliccolloid-silver iodobromide emulsion layer which contains 0.0015 to 0.03gram of a lower monoalkylaminomonohydroxybenzene per 100 grams of silverhalide.

6. A photographic element bearing at least one hydrophiliccolloid-silver bromide emulsion layer which contains 0.0015 to 0.03 gramof N-alkylaminomonohydroxybenzene having from 1 to 2 carbon atoms in thealkyl group per 100 grams of silver halide.

7. A photographic element bearing at least one hydrophiliccolloid-silver iodobromide emulsion layer which contains 0.0015 to 0.03gram of N-alkyl-para-aminophenol having from 1 to 2 carbon atoms in thealkyl group per 100 grams of silver halide.

8. A photographic element bearing at least one gelatino-silveriodobromide emulsion layer which contains 0.0015 to 0.03 gram ofN-methyl-paraaminophenol sulfate per 100 grams of silve halide.

, RALPH KINGSLEY BLAKE.

, REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Great Britain 1898

